New to iOS looking for Help with Files

I am trying to move some of my workflows from a phone to a tablet. The android tablets I’ve used, I just don’t like or trust them. I purchased an Ipad at the recommendation of a friend. However, I am terribly frustrated at the moment.

My issue is file management. I use Google drive for my working storage. However, I am not able to download any files to my iPad. If I try and post a video I’ve worked on from my computer, from my google drive I have on my iPad it fails on every platform I try to upload to. I figured this was due to it not being on the iPad and trying to be a point of handoff between to services. So I wanted to download the video to my iPad and upload it that way, but I cannot figure out how to do this. I tried some 3rd party apps but their folders are not seen by installed apps.

I’m at a loss of what to do, and I’m hoping this is me just not being familiar with iOS, and I am missing something. I am tied to google services for my purpose. Anyone explain how I am missing a simple step?